Prior Art
Nickel electrodes made for long lived nickel-cadmium alkaline batteries and the like desirably exhibit high energy density and a high percentage of active material. Typically, such nickel electrodes are formed by impregnating porous sintered nickel bodies known as plaques with active nickel material, that is, nickel hydroxide. A well-known deposition procedure consists of filling the pores of the plaque with an aqueous solution of nickel-bearing salts or with molten nickel salt, usually with the aid of a vacuum. The nickel-bearing salt is then converted in the pores of the plaque to nickel hydroxide by treatment with an alkaline solution. This procedure requires a number of repetitions in order to build up the level of nickel hydroxide within the pores to a concentration which makes the product commercially acceptable. If the plaque is allowed to corrode, the number of repeates of the procedure is decreased but the plaque structure is weakened.
Kandler in U.S. Pat. No. 3,214,355 carried out the impregnation procedure in an electrochemical mode. Kandler used room temperature treatment which did not result in sufficient ultimate impregnation to make a successful nickel product. Meuller (U.S. Pat. No. 3,203,879) carried out the electrochemical deposition from a molten salt. Pell and Blossom in U.S. Pat. No. 3,507,699 disclosed an electrochemical process using an acidic aqueous solution of nickel nitrate at elevated temperatures to provide loading levels up to about 7.7 AH/in..sup.3 of plaque, equal to or greater than the best loading levels previously produced.
It would be desirable to find a way of improving the method of Pell and Blossom so as to further increase the loading levels obtainagle therefrom while decreasing plaque corrosion and improving control of the level of impregnation. It is also important to substantially limit the thickening and stressing of the plaque which normally occurs at high loading levels. Such a technique should result in improving the overall plaque quality, while reducing its variability, decreasing its sensitivity during processing to temperature fluctuations and increasing its maximum loading level.